Why does my Xamarin PCL throw a runtime exception when Building release for Universal App?

Question

I have a xamarin PCL that builds fine in x86 Debug mode. When I switch it to Release Mode (x86 or x64) or x64 Debug, I am getting runtime exceptions. It probably relates to

https://forums.xamarin.com/discussion/57810/issue-with-xamarin-forms-in-windows-uwp-app-compiled-in-the-release-mode

but I don't know what other assembly I'm using. How can I tell?

My computer is x64. When I run x64 in either debug or release I get

Exception "System.NotImplementedException" in MyApp.Interop.dll. Additional Info Arg_NotImplementedException.

Before entering the constructor App(). The call to the constructor is here:

LoadApplication(new MyApp.App());

When I build x86 I get a little bit further. It gets into the MyAppConstructor and calls the xaml constructor and gives exception:

System.Reflection.MissingMetadataException in System.Private.Reflection.Core.dll AdditionalInfo:Arg_InvokeMethodMissingMetadata, System.EventHandler. For more information, visit http://go.microsoft.com/fwlink/?LinkId=623485

So it looks like a Xaml assembly I'm missing. How do I find out what assembly I need to add?

I put it back on Debug, but turned it to "use the Native Compiler" so I could get more details on the exceptions:

x86: Additional information: Cannot create a delegate on type 'System.EventHandler' as it is missing metadata for the Invoke method. For more information, please visit http://go.microsoft.com/fwlink/?LinkID=616867

x64: An exception of type 'System.NotImplementedException' occurred in Xamarin.Forms.Platform.UAP.dll but was not handled in user code

Additional information: The method or operation is not implemented.

UPDATE: I am guessing x64 is not supported in Xamarin because no mobile product has x64 processor? Still leaves the problem with the x86 release. I have tried adding the following assemblies in my Universal App.xaml.cs

  List<Assembly> assembliesToInclude = new List<Assembly>();
  assembliesToInclude.Add(typeof(MyApp.MyAppMainPage).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.ImageSource).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.StackLayout).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.Label).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.Button).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.FormattedString).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.Span).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.Image).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.ScrollView).GetTypeInfo().Assembly);
  assembliesToInclude.Add(typeof(Xamarin.Forms.WebView).GetTypeInfo().Assembly);
  // add this line
  Xamarin.Forms.Forms.Init(e,assembliesToInclude); // requires the `e` parameter

where MyAppMainPage is the xaml page I try to load in my PCL and the rest are the UI elements that the page is made up of.

I now see this Exception thrown for x86:

'System.PlatformNotSupportedException' in System.Private.Interop.dll Exception thrown: 'System.AggregateException' in System.Private.Threading.dll Exception thrown: 'System.Reflection.MissingMetadataException' in System.Private.Reflection.Core.dll

Why would the platform not be supported? Xamarin supports Universal right?

Looks like you're trying all the right things, obviously you've cleaned and deleted all files in bin folder? Is there any clues by turning up the build log verbosity and comparing debug vs release — Jeremy Thompson
In Visual Studio go to Tools->Options then find the Project and Solutions->Build and Run node. — Jeremy Thompson
@JeremyThompson That seems to give me more data when building, but not sure I'm getting anything more during runtime. I did catch one more exception which I have added — Seth Kitchen
Weird PlatformNotSupportedException, if it works it debug it should be supported in release — Jeremy Thompson

Seth Kitchen Seth Kitchen · Accepted Answer · 2015-12-23T14:55:46

I have added a Directives file. Add a file with .rd.xml ending. Mine was MyApp.rd.xml. Then include the types the exception says are missing. Mine was System.EventHandler. Here is my code (you probably don't need the other two).

<?xml version="1.0" encoding="utf-8"?>
<Directives xmlns="http://schemas.microsoft.com/netfx/2013/01/metadata">
<Application>
  <Type Name="MyApp.MyAppMainPage" Dynamic="Required All" /> 
  <Type Name="System.EventHandler" Dynamic="Required All" /> 
  <Namespace Name="System.Private.Reflection.Core" Serialize="Required All" />
</Application>
</Directives>

I guess in Universal Apps for Xamarin you need to include the assembly when loading embedded resources. I had to change

ImageSource.FromResource("MyApp.Images.Sign.jpg");

to

var assembly = typeof(MyAppMainPage).GetTypeInfo().Assembly;
ImageSource.FromResource("MyApp.Images.Sign.jpg",assembly);

You can check what resources you have by

foreach (var res in assembly.GetManifestResourceNames())
  System.Diagnostics.Debug.WriteLine("found resource: " + res);

x64 still broken.

Why does my Xamarin PCL throw a runtime exception when Building release for Universal App?

1 Answers